The one in Will's video looks to be 25W resistor, but 100% sure.
for 48V (it is actually around 55V), if you use 25 Ohms resistor, the max current will be 48V/25 Ohms = 1.9A so power dissipation on the resistor will be about 48V x 1.9A = 92W but it will be really really short duration so really no need to use 100W resistor, 50W will be fine, it takes 5 Tc (Time constant, you can look up RC time constant to learn about it) to charge the capacitor to the applied Voltage.
You can use 47 Ohms resistor in 12V/24V/48V with no issue, the resistor is used to limit the in-rush current, the time it takes to full charge the capacitor banks depend on the value of the resistor and the capacitance of the capacitor bank.
BTW, when perform pre-charge, the inverter power switch should in the OFF position.